JPH0771955A - Distance measuring system - Google Patents

Abstract

PURPOSE:To accurately measure the distances to a plurality of points within a screen by providing first and second light projectors and receiver means arranged at intervals of the length of a base line from each other, and a computing means for computing the distance to a subject to be photographed in accordance with a light projection signal during scanning by the projector means. CONSTITUTION:A CPU1 controls a distance-measuring projector portion 2 with respect to a subject to be photographed and also controls a scanning portion 3 that scans the projector portion 2. A light position sensing device (PSD) 5 is located behind a light receiving lens 4 and a PSD 7 is located behind a light receiving lens 6, the outputs of the PSDs 5 and 7 being inputted to the CPU1 via respective light position detector circuits 8 and 9. A distance-measuring light beam projected by the projector portion 2 is reflected on the subject to be photographed and forms light spots on the PSDs 5, 7 via the two lenses 4, 6. The positions of incidence of the light spots are computed by the circuits 8, 9 in accordance with the signals outputted by the two PSDs 5, 7. The CPU 1 computes the distance to the subject to be photographed from the outputs of the circuits 8, 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device, and more particularly to a distance measuring device for a camera which projects a distance measuring light on an object to obtain the distance to the object.

[0002]

2. Description of the Related Art Heretofore, many attempts have been made to focus an object existing in other than the central portion of a photographic screen with one touch. For example, JP-A-58-201
Japanese Patent No. 05 discloses a technique in which a plurality of light projecting elements are prepared, and the light is sequentially projected to enable distance measurement at a corresponding point on the screen.

However, in this method, as the number of distance measuring points in the screen is increased, more light emitting elements are required, resulting in an increase in cost. Therefore,
It has been attempted to measure the distance to each point on the screen by scanning one light projecting element. For example, there is a technique of displacing the relative position between the light projecting lens and the light projecting element in the old US Pat. No. 4,470,681.
Recently, a similar proposal has been made to Japanese Patent Laid-Open No. 64-57246.

[0004]

However, when the relative positions of the light projecting / receiving lens and the light projecting / receiving element are changed as described above, there is a problem that rattling occurs and an erroneous distance measurement is likely to occur. Therefore, Japanese Patent Laid-Open No. 59-107332 discloses a technique for improving such erroneous distance measurement by scanning the light emitting / receiving element and the lens in a unit state.

However, in order to move the entire unit including the light emitting / receiving element and the lens, not only the actuator becomes large and the mechanism becomes complicated, but also the scanning speed becomes slow and the time lag for distance measurement becomes long. It caused problems. The present invention has been made in view of the above problems, and an object of the present invention is to provide a distance measuring device that can measure a plurality of points on a screen with high accuracy and at high speed.

[0006]

That is, the present invention is directed to a light projecting means for projecting a light beam toward an object, and first and second light projecting means.
Of the first and second light receiving means, which are arranged with the base line of the light source spaced apart from each other, receive the reflected light of the light flux from the subject, and output signals according to the incident position, and the scanning for scanning the light projecting means. And a calculating means for calculating the distance to the subject based on the signal when the scanning means scans the light projecting means.

Further, according to the present invention, a light projecting means for projecting a light beam toward an object and a position separated from the light projecting means by a first predetermined base line length are provided, depending on an incident position of reflected light from the object. A pair of first light receiving elements that output a pair of first signals, and a pair of second signals that are arranged at a position separated from the light projecting means by a second predetermined baseline length and that correspond to the incident position of the reflected light from the subject. A second light receiving element that outputs a signal, a first calculation unit that calculates a ratio of the pair of first signals, a second calculation unit that calculates a ratio of the pair of second signals, and the first calculation unit. And an integrating circuit for adding and integrating the ratio calculations output from the calculating means and the second calculating means, respectively.

Further, the present invention further comprises a correction means for electrically correcting a variation in at least one of the output characteristics of the first calculation means or the second calculation means for performing the ratio calculation. Characterize.

[0009]

In the distance measuring apparatus of the present invention, the luminous flux is projected from the light projecting means toward the subject. Then, the reflected light from the subject of the light flux is received by the first and second light receiving means that are arranged with the first and second baseline lengths separated from each other.
A signal is output depending on the incident position. The light projecting means is scanned by the scanning means. When the light projecting means is scanned by the scanning means, the distance of the subject is calculated by the calculating means based on the signal.

Further, in the distance measuring device of the present invention, a light beam is projected from the light projecting means toward the subject. Then, the pair of first signals corresponding to the incident position of the reflected light from the subject is generated by the first and second light receiving elements which are arranged at positions separated from the light projecting means by the first and second predetermined base line lengths. The second signal is output. The first and second calculating means perform a ratio calculation of the pair of first signals and a ratio calculation of the pair of second signals. Then, the ratio computations respectively output from the first computing means and the second computing means are added and integrated by an integrating circuit.

Further, in the distance measuring apparatus of the present invention, the correction means electrically corrects a variation in at least one of the output characteristics of the first calculation means or the second calculation means for performing the ratio calculation. It

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the concept of a distance measuring device according to a first embodiment of the present invention. In the figure, the CPU
Reference numeral 1 controls a light projecting unit 2 which is a unit for projecting distance measuring light to a subject and a scanning unit 3 which scans the light projecting unit 2. Further, a light position detecting element (P
SD) 5 is located, and similarly P is behind the light receiving lens 6.
SD7 is located. The outputs of these PSDs 5 and 7 are input to the CPU 1 via the optical position detection circuits 8 and 9, respectively.

In such a structure, from the light projecting section 2,
Distance measuring light is projected onto a subject (not shown). At this time, the light projecting unit 2 is controlled to be scanned by the CPU 1 via the scanning unit 3 so that the light projecting direction is changed. As a result, the distance can be measured at each point on the screen.

The distance measuring light projected by the light projecting unit 2 is reflected on a subject (not shown) and forms light spots on the PSDs 5 and 7 via the two light receiving lenses 4 and 6, respectively. Based on the output signals of these two PSDs 5 and 7,
The light position detection circuits 8 and 9 calculate the incident position of the light spot. Then, the CPU 1 calculates the subject distance from the outputs of the light position detection circuits 8 and 9.

FIG. 2 shows the distance measuring principle of the distance measuring device of the present invention. In the figure, reference numeral 10 denotes a distance measuring light spot projected on a subject, and light receiving lenses 4 and 6 are arranged at a position separated from the distance measuring light spot 10 by a distance L. The PSDs 5 and 7 are arranged behind the light receiving lenses 4 and 6. Further, the distance between the light receiving lenses 4 and 6 and the PSDs 5 and 7 is f _J , and the PSD 5 and
Assuming that the light spot positions on 7 are x ₁ and x ₂ with reference to the optical axis of each lens, the following relational expression holds.

L: f _J = S ₁ : x ₁ L: f _J = S ₂ : x ₂ S ₁ = L × x ₁ / f _J (1) S ₂ = L × x ₂ / f _J (2) ) S = S ₁ + S ₂ = (L / f _J ) (x ₁ + x ₂ ) ... (3) L = (S · f _J ) / (x ₁ + x ₂ ) ... (4) Therefore, depending on the PSD 5 and 7, x _{When 1} and x ₂ are detected, S and f _J have fixed values, so that the distance L can be obtained.

Therefore, accurate distance measurement can be performed regardless of the position of the distance measuring light spot 10. Next, a second embodiment in which the distance measuring device of the present invention is applied to a camera will be described. Figure 3
FIG. 6 is a block diagram showing a configuration of a second exemplary embodiment of the present invention. In the above-described first embodiment, the one-dimensional position detection type PSDs 5 and 7 are used, but in the second embodiment, a mechanism of two-dimensionally scanning the IRED is adopted, and the PSD is also used. A device that can detect two-dimensional position is used. Therefore, according to the embodiment, it becomes possible to deliver the light projecting point (distance measuring light point) within the camera screen.

First, the mechanism for two-dimensionally scanning the IRED will be described. The IRED 11 is driven and controlled by the CPU 1 via the IRED driver 12, and a light projecting lens 13 is arranged in front of it. The IRED 11 is attached to the IRED holder 14, and the guide rail 1 is driven by a motor 16 driven by a motor (M) driver 15 and a feed screw 17.
Slide in the x direction shown in FIG. Also, IRED
The motor 11 and the IRED holder 14 slide along the guide rail 23 along the guide rail 23 in the y direction in the figure by the motor 20 and the feed screw 21 driven by the motor (M) driver 19.

On the other hand, PSDs 5 and 7 capable of two-dimensional position detection are arranged behind the light-receiving lenses 4 and 6 which are arranged at a distance of the base line length S, respectively. And P
SD5 outputs the optical position detection circuits 8a and 8b to the PSD
The output of 7 is supplied to the CPU 1 via the optical position detection circuits 9a and 9b, respectively. Incidentally, reference numeral 24 is a switch for inputting the start timing of distance measurement, which is also commonly used as a release switch.

FIG. 4A is an external view showing an arrangement in which the distance measuring device shown in FIG. 3 is incorporated in a camera. Figure 4
In FIG. 3A, a release switch 24 is provided on the upper surface of the camera body 25. In front of this camera,
A photographing lens 26 is provided in the substantially central portion thereof, and a window of a finder 27 and a projection lens 1 of the distance measuring device are provided in the periphery thereof.
3, the light receiving lenses 4 and 6 are arranged as shown in the drawing.

In such a configuration, the M driver 15
When the motor 16 rotates by, the IRED holding unit 14
Along the guide rail 18 by the feed screw 17
Slide in the direction. The support 22 is movable along the guide rail 23, and the motor 20 driven by the M driver 19 rotates the feed screw 21 to scan the IRED 11 in the y direction. C
The PU 1 controls the M drivers 15 and 19 according to a predetermined sequence, and causes the IRED 11 to emit light via the IRED driver 12.

The distance measuring light from the IRED 11 is projected by a light projecting lens 13 onto a subject (not shown). Since this distance measuring light is projected in the direction connecting the position of the IRED 11 and the principal point of the light projecting lens 13, each time the position of the IRED 11 moves in the x and y directions, it is shown in FIG. As described above, the distance measuring point 28 on the photographic screen (finder) changes two-dimensionally.

On the other hand, in synchronization with the light emission of IRED11, 2
From the outputs of the two PSDs 5 and 7, the positions of the reflected signal light from the subject incident on the PSDs 5 and 7 via the light receiving lenses 4 and 6 are detected by the optical position detection circuits 8a, 8b, 9a and 9b. The CPU 1 uses these optical position detection circuits 8a, 8
From the outputs of b, 9a, and 9b, the distance to the subject at each point on the screen is calculated.

Here, regarding the optical position detection circuit of FIG.
This will be described with reference to FIG. Output currents i ₁ and i ₂ are output from both ends of the PSD 30, respectively, and are output to the preamplifiers 31 and 3 respectively.
2. N that constitutes a differential operation circuit together with the constant current source 37 via the compression diodes 33 and 34 and the buffers 35 and 36.
It is supplied to the bases of the PN transistors 38 and 39. The transistors 38 and 39 have their emitters commonly connected and are connected to the constant current source 37. Also, the transistor 39
The collector of is connected to the power source via the integrating capacitor 40, and is also connected to the CP via the switch 41 and the terminal 42.
It is connected to U1. A background light removing circuit 43 for removing the current of the background light is connected to the output of the PSD 30.

Now, it is assumed that the signal light is incident on the PSD 30 having the length t at the position of x as shown in FIG. Two
The two output currents i ₁ and i ₂ depend on the light positions x and t and satisfy the relationship of i ₁ / (i ₁ + i ₂ ) = x / t (5).

However, the PSD 30 has incident background light in addition to the signal light, and i ₁ and i _{2 in} the above equation (5) cannot be obtained without removing the background light. Therefore, the background photocurrent removing circuit 43 is connected to the output of the PSD 30.

The signal photocurrents i ₁ and i ₂ are supplied to the preamplifier 3
It is amplified by β times by 1, 32 and flows to the compression diodes 33, 34 as shown in FIG. The voltage generated in the compression diodes 33 and 34 is transferred to the buffers 35 and 36.
Is input to the differential operation circuit. The constant current source 30 controlled by the CPU 1 causes a current of I ₀ to flow in synchronization with the emission of IRED, that is, the incidence of signal light. On the other hand, the integrating capacitor 40 has its potentials at both ends equalized to Vcc by the switch 41 before the IRED emits light. The switch 41 is turned off in synchronization with the light emission of IRED.

With the circuit thus configured, the PSD
The relationship between the output currents i ₁ and i _{2 of} 30 and I _{INT is} as follows: I _INT = (i ₁ / (i ₁ + i ₂ )) × I ₀ = (x / t) I ₀ (6) Since this current I _INT is integrated in the integrating capacitor 40 for a predetermined time, by detecting the voltage at the terminal 42, the CPU 1 obtains x = t · I _INT / I ₀ (6) ′ according to the above equation (6). The signal light incident position x can be calculated.

Optical position detection circuits 8a, 8 shown in FIG.
b, 9a and 9b detect the position of light based on such a principle. Next, a method for obtaining the subject distance L from the signal light positions on these PSDs will be described with reference to FIG.

In the example of FIG. 2 described above, the principle of distance measurement has been described for the one-dimensional projection scan in the x direction, but here, the change in the y direction of the distance measurement point is also taken into consideration.
This is an example of AF corresponding to a two-dimensional light projection scan. That is, when the angle θ formed between the optical axes of the light receiving lenses 4 and 6 in FIG. 6A and the distance measuring point is θ = 0, the above equation (4) described in FIG. 2 is established.

In FIG. 6 (a), since L ₁ = S · f _J / (x ₁ + x ₂ ) (7) from the above equation (4), L = L ₁ cos θ (8) Yes, if θ is detected, then x can be combined with the above equation (7).
It is clear that the subject distance L can be obtained from ₁ and x ₂ .

The distance-measuring light projected from the light projecting lens 13 toward the object 44 is obtained by arranging the light receiving lenses 4 and 6 as shown in FIG. 4A, and further regarding the two-dimensional PSDs 5 and 7. Direction (x) connecting the principal points of the two light-receiving lenses 4 and 6
And when the y direction is arranged so that the y direction perpendicular to it can be detected, as shown in FIG. 6 (b),
A light spot is connected on the two PSDs 5 and 7.

When the distance between the two sets of light receiving lenses and the PSD is both f _J , the positions 45 and 46 on the PSD of the lens optical axis are set.
The following relational expression is established between the position y ₁ of the light spot in the y direction with reference to and the above θ. tan θ = y ₁ / f _J (9) From this relationship, the subject distance L can be calculated from the light spot positions in the x and y directions, x ₁ , x ₂ and y _{1 as} follows. . L = (S · f _J / (x ₁ + x ₂ )) · cos (arctan (y ₁ / f _J )) (10) Therefore, as shown in FIG. 3, the two-dimensional PSD 5,
From the output of 7, the CPU 1 and the optical position detection circuits 8a, 8b, 9
a, 9b and x ₁ , x ₂ , y ₁ are calculated,
The CPU 1 can obtain the subject distance according to the above equation (10).

As the optical position detection circuit, the one described in FIG. 5 is used. Although y ₁ can be detected by any PSD, the detection accuracy of y ₁ is increased by assuming a flowchart such as that shown in FIG.

Next, the scan AF operation of this range finder will be described with reference to the flow charts of FIGS. In FIG. 7, step S1 is the motor 1 of FIG.
This is a step of reversing 9 and 20 to initialize the position of the IRED 11. At the same time, set this position to M = 0, N = 0
And Next, in step S2, the first distance measurement coordinate in the y direction is determined. Then, in step S3, it is determined whether or not the number of points measured by scanning distance measurement exceeds M ₁ .

If the number of measured points does not exceed M ₁ , the process goes to step S4 to scan the IRED 11 by a predetermined amount in the x direction. Then, M is incremented in step S5, distance measurement is performed in step S6, and the process returns to step S3. In this way, in steps S3 to S6, as shown in FIG. 4B, the distance measurement at M ₁ points in the x direction is sequentially performed.

When it is determined in step S3 that the scanning in the x direction has been performed once, the process branches to step S7 for determining the next distance measuring y coordinate. Then, after N is incremented in step S8, it is determined in step S9 that the number of points measured by scan distance measurement becomes N ₁ .

If the number of points measured by scanning distance measurement does not exceed N ₁ , the process proceeds to step S10 and the position in the x direction is reset. Then, in step S11,
The value of M is also initialized and the process returns to step S4 to perform the distance measurement at M _{1 position} in the x direction described above. This is repeated until the distance measurement at N _{1 positions in the} y direction is completed in step S9. Then, in step S12, the obtained distance measurement results L _{11 to} L
_Focus on the closest distance measurement result than _M1N1 .

According to this flowchart, as shown in FIG. 4B, it is possible to arrange M ₁ × N ₁ distance measuring points in the photograph screen. By the way, two-dimensional P
It is difficult to detect the optical positions in the x direction and the y direction at the same time by SD. Therefore, in this embodiment, the IRED is caused to emit light twice, and the light position coordinate in the x direction and the light position coordinate in the y direction are detected each time. However, different PS
The position detection circuit connected to D can be operated simultaneously.

Therefore, in the distance measuring subroutine in step S6 of FIG. 7, PSD is performed at the same timing as in steps S22 and S23 and steps S28 and S29.
It is clearly shown that the light position detection from each of 5 and 7 is performed.

In FIG. 8, first, in step S21, I
The RED 11 starts to emit light, and the optical position detection circuits 8a, 8
b, 9a, 9b, the signal light incident position x ₁ in the x direction at the same timing as in steps S22 and S23,
Find x ₂ . Specifically, the respective light position detection circuits 8a, 8
A voltage depending on the above equation (6) is generated and held in the integrating capacitors b, 9a and 9b (40 in FIG. 5).
Then, in step S24, it is determined whether the integration into the integration capacitor has been completed for a predetermined time. Here, after the integration is completed, the light emission of the IRED 11 is completed in step S25.

Next, the IRED 11 is made to emit light again,
In order to prevent the deterioration of the light amount due to the rise in the chip temperature of the IRED 11 due to the continuous light emission, a predetermined time interval is set by the timer in step S26. In step S26, the CPU 1 sets the integrated voltage held by the integrating capacitor in steps S22 and S23 to A /
Read it after D conversion.

Next, in step S27, the IRED11 is again used.
Made to emit light, y-direction of the signal light incidence position y _15, y ₁₆ and optical position detecting circuit 8b in step S28 and S29, is detected by 9b.

Similar to the detection in the x direction described above, step S
When the integration for a predetermined time is completed at 30, the process proceeds to step S31 and the light emission of the IRED 11 is completed. Then, in step S32, the integration result is read again, and the signal light positions y ₁₅ and y obtained as described in the above equation (6) ′ are calculated.
₁₆ is averaged as in step S33 to reduce the measurement error. From y ₁ and x ₁ and x ₂ thus obtained, in step S34, the above (10)
The subject distance is calculated using an arithmetic expression as described in the equation.

In the flow chart described above, FIG.
Although the distance measurement is performed as shown in FIG. 9A, the distance measurement point is not limited to this, and the distance measurement point may be changed as shown in FIG. 9B, for example. According to the example shown in FIG. 9B, there is an advantage that the distance measuring time can be further shortened.

With such a distance measuring device, as shown in FIG. 10, even in a scene in which the subject does not exist at the point of the center portion 47 of the screen 27, the main subject 44 can be correctly captured.
It is possible to focus on.

As described above, according to the present embodiment, it is possible to provide a camera having a simple structure, which can measure a plurality of points on the screen with high accuracy and high speed and can easily take a photograph of correct focus. it can.

Further, according to this embodiment, since the distance can be measured according to the equation (10) without any relation to the rattling of the movable part of the IRED, a means for strict scanning position detection is unnecessary. . That is, when the IRED is initialized as in step S1 of the flowchart of FIG. 7, it is only necessary to properly detect the position thereof, and the subsequent predetermined amount of scanning may be controlled by the energization time to the motor. The conventional active triangulation method with the base line as the base length does not require strict positioning as in the case of scanning the light projecting unit.

As shown in FIG. 11, if the main subject 44 exists in the center of the screen and the focus is simply focused on the closest subject, the miscellaneous subject 48 will be in focus and the main subject 44 will be in focus. Since there are many scenes where the focus becomes unfocused, a main subject selection flowchart may be considered in which only the distance measurement result at the center of the screen is treated specially. For example, when there is no scenery at the center of the screen and there is only a landscape, the distance measurement result at the center of the screen shows a value of infinity, so an algorithm for selecting the closest distance only at this time is conceivable.

As described above, according to the present invention, the distance measurement result at the center of the screen can be selected even without the strict positioning means.
Will be described with reference to.

FIG. 12 (a) is a third embodiment of the present invention and is a front view showing an arrangement in which a distance measuring device is incorporated in a camera. A release switch 24 is provided on the upper surface of the camera body 25. Further, on the front surface of the camera, a photographing lens 26 is provided in the substantially central portion thereof, and a window of a finder 27, and a light projecting lens 13 and light receiving lenses 4 and 6 of a distance measuring device are provided in the periphery thereof as illustrated. It is arranged.

FIG. 12B is a conceptual view of the camera of FIG. 12A as seen from above. In the figure, two light receiving lenses 4 and 6 are arranged side by side with respect to the finder objective lens 27. Here, if only the x-coordinate is considered, the center of the camera screen is at the position of 47 in the figure, but if the y-direction is not considered, the distance measurement light obtained when the distance measuring light is projected from this point to the point It can be said that the distance measurement result is the distance measurement result at the center of the screen.

Therefore, the distance between the principal points of the finder objective lens 27 and the light receiving lens 4 is S _2x (FIG. 4A).
Then, from the distance f _J between the light receiving lens and the PSD, the following relationship holds between the signal light receiving position x ₁ on the PSD ₇ and the distance L.

X ₂ = ((S + S _2x ) · f _J ) / L (11) The signal position x ₁ on the PSD 5 may be used, but in general,
Since the baseline should be long, use x ₂ .

If only the y coordinate is considered, FIG.
As shown in. In the figure, if 13 is a projection lens, 11 is an IRED, and 27 is a viewfinder objective lens, the reflected signal light incident from the subject in the center of the screen will be transmitted to the y ₁ position of the PSD 7 via the light receiving lens 4. Connect the points. At this time, the signal receiving position y _{1 in} the y direction on the PSD ₇
Satisfies the following relationship with the distance L.

Y ₁ = (S _2y · f _J ) / L (12) where S ₂ is the lens 2 as shown in FIG. 4 (a).
7 and the y-direction component of the distance between the principal points of the lens 4.

S + S _2x = 30 mm, f _J = 20 mm, S
_{When 2y} = 30 mm, the equations (11) and (12) become x ₂ · L = y ₁ · L = 600 mm ² (13)

FIG. 13 is a flow chart for explaining the operation of the third embodiment in which the distance measurement result L _MNO at the center of the screen is emphasized. In the flowchart of FIG. 13, steps S1 to S11 are the same as steps S1 to S11 of FIG. 7 described above, and therefore description thereof will be omitted.

If the number N of points scanned and measured exceeds N ₁ in step S9, the process proceeds to step S13, and is obtained according to the principles described in the equations (11) and (12). The distance measurement result at the center of the screen is determined from the distance L _MN and the light incident positions x ₂ and L ₁ at that time. The determination numerical value here is based on the above equation (13). The inequalities are due to variations in the optical position detection circuit and IRED.
This is because there is an error in the scan position.

Next, in step S14, the distance measurement result L _{MNO at the} center of the screen thus obtained and the predetermined distance L ₁
To compare. Here, for example, when the distance is closer than L ₁ = 5 m, the subject in the center is considered to be the main subject, so the process branches to step S15 to focus on the distance measurement result L _MNO at the center of the screen. . On the other hand, L ₁ = 5m
In the case of the above long distance, it is determined that the main subject does not exist in the center of the screen, and the process branches to step S16. Then, as in step S12 of FIG. 7, in step S16, the closest distance is selected from the obtained distance measurement results of M ₁ × N ₁ , and the focus is adjusted here.

In such an embodiment, it becomes possible to correctly focus on the person who is the main subject even in the scene shown in FIG. By the way, as shown in FIG. 14, the positional relationship between the finder lens 27 of a general conventional camera and the light projecting means (IRED11, light projecting lens 13) is fixed, and the screen at the position shown by 27a is fixed. Although the distance can be measured at the central portion, the distance at the central portion of the screen cannot be measured for the screen at the position indicated by 27b. This is referred to as a parallax error between the distance measuring system and the finder system, but such a problem of parallax can be dealt with in the third embodiment described above.

Further, in the above description, the IRED scan mechanism shown in FIG. 3 is assumed as an example of the optical scanning for distance measurement, but the present invention is not limited to this, and for example, FIGS. 15 (a) and 15 (b) are used. It is also possible to substitute the mechanism shown in. That is, FIG. 15A shows the projection lens 13
The IRED 11 and the IRED 11 are integrated, and the structure of a unit 50 that is rotatable around a fulcrum 49 is shown. In addition, FIG.
(B) is an IRED projected through the projection lens 13.
11 shows a mechanism in which the distance measuring light 11 is reflected by a mirror 52 that is rotatable around a fulcrum 51.

In the above-mentioned embodiment, the PSD is used for the optical position detecting element, but the present invention is not limited to this, and the 2-split SPD may be used. Next, a further embodiment of the present invention will be described with reference to FIGS.

In FIG. 16, the IRED 53 is arranged in the vertical direction of the PSDs 54 and 55 having a size represented by a length t and a width w, that is, in the middle of the y direction in the drawing. Then, in front of the IRED 53, PSD 54 and 55, a light projecting lens 56 and a light receiving lens 57 and 58 are respectively provided.
Are arranged vertically. The distance measuring light 59 projected from the IRED 53 via the light projecting lens 56 can be changed in its projection direction (θ _x ) by the scanning device 60. Further, the scan position is input to the CPU 62 by the position detection circuit 61.

The reflected signal light received through the light receiving lenses 57 and 58 is received by the PSDs 54 and 55, and the light receiving position thereof is detected by the AF circuit 63. A value for correcting the distance measurement result is obtained from the tilt adjusting circuit 64, which will be described later, in the AF circuit 63.

The CPU 62 is an electrically rewritable memory EEP that stores the adjustment values of the apparatus.
The ROM 65 is connected. FIG. 17 is an external view of a camera equipped with the distance measuring device having such a configuration. In the figure, a release switch 67 is provided on the upper surface of the camera body 66. On the front surface of the camera, a taking lens 68 is arranged in the substantially central portion and a finder objective lens 69 is arranged above the photographing lens 68. Further, a light receiving lens 57 is arranged in the peripheral portion of the taking lens 68 adjacent to the finder objective lens 69, and a light projecting lens 56 and a light receiving lens 58 are arranged below the light receiving lens 57 as shown in the figure. There is. Incidentally, 70 represents a strobe.

Next, the operation of the two PSDs of the distance measuring device having such a configuration will be described with reference to FIG. PSD54
Can measure the position of the optical signal incident from the range of θ ₅₇ via the light receiving lens 57. On the other hand, the PSD 55 can measure an optical signal from the range of θ ₅₈ via the light receiving lens 58. Therefore, the positions of the light spots at which the two PSDs can be measured at the same time are in the range of θ _y shown by the shaded area E in FIG. That is, if the distance from the PSD end to the optical axis of the light receiving lens is a and the focal length is f _J , θ _y is (1
It is expressed as in equation 4).

[0068]

[Equation 1] If f _J = 16 mm and a = 0.3 mm, then θ
_y is only about 2 °.

On the other hand, as shown in FIG.
Considering the widths w of 4, 55, the detectable range θ _x of the light spot in the x direction in the figure is θ _x = arctan (w / f _J ) ... (15), and if w = 3 mm and f _J = 16 mm, θ _x becomes 10.6 °. In order to widen θ _y here, a
It is possible to increase P, but if a is increased, P
The length t of SD becomes large and the resolution of AF deteriorates.

Considering in this way, when trying to measure many points on the photographic screen with this range finder, y
It can be seen that a wider range can be supplemented in the x direction than in the direction. FIG. 18B shows the y-direction light spot positions incident on the PSDs 54 and 55 when the distance measuring light 59 moves in the y direction at the same distance. As shown in FIG. 18 (a), at positions where light is symmetrically incident on both PSDs,
Light spot position 5 on PSD by output of each PSD 54, 55
4a and 55a intersect. Light receiving lens 57, 58 and PS
If D54 and D55 are arranged symmetrically and the circuits that process the outputs of the two PSDs have exactly the same characteristics, 5
A correct distance measurement result can be obtained by adding the results of 4a and 55a.

It should be noted here that if the arrangement of the circuit and each element becomes unbalanced, the slope of the output of each PSD becomes unbalanced as shown by the straight line 55b, and the above addition causes It means that the correct distance measurement result cannot be obtained. To correct this electrically
It is the tilt adjustment circuit 64 described above.

FIG. 18C shows y on each PSD 54, 55 when the distance measuring light 59 moves in the x direction at the same distance.
The light spot position in the direction is shown. Since there is no change in the y direction, the output is ideally constant as shown in the figure.

Therefore, the distance measuring device having the configuration shown in FIG.
Under the above constant conditions, 10 ° in x direction and 2 ° in y direction
Two PSDs for distance measuring light incident from the range
The distance can be measured according to the output of.

With such a distance-measuring system, correct focusing is performed on the distance-measuring light reflected from the area E ′ of 2 ° × 10 ° in the screen as shown in FIG. Is possible. Therefore, even when the distance measuring light spreads out as shown in FIG. 19 and protrudes from the subject, there is an advantage that the distance can be correctly measured as long as the reflected light returns.

In particular, for a long-distance subject, the projected spot diameter φ _T becomes large in proportion to the distance L according to the relationship of the equation (16). Therefore, φ _T tends to be larger than the face size φ _F. φ _T = (φ _LED / f _T ) L (16) where f _T : focal length of projection lens φ _LED : emission diameter of IRED In general active triangulation method, φ _F > φ _T Only the correct distance can be measured, but according to the embodiment,
As described above, part of the distance measuring light is reflected from the subject and
There is a merit that correct distance measurement becomes possible when the light is incident on two PSDs.

Next, the embodiment will be described in more detail with reference to FIG. IRED53 is the IRED driver 7
The light emission control is performed by the CPU 62 via 1, and is attached to the movable member 72. This IRED53 is
The motor 73 and the feed screw 74 are movable in the x direction in the figure, and the motor 75 and the feed screw 76 are movable in the y direction. Then, the CPU 62 causes the motor (M) driver 7
By controlling the rotation of the motors 73 and 75 via 7, 78, the relative position between the IRED 53 and the light projecting lens 56 can be controlled.

The initial position switch 79 is for detecting the initial position of the IRED 53, and the CPU 62 depends on how much each motor rotates from this initial position.
Detects the position of the IRED 53. I
Since the direction of the light ray passing through the light projecting lens 56 changes depending on the position of the RED 53, the distance measuring light projecting point 59 can be changed as shown in FIG. CPU6
2, while changing the position of IRED53 in this way,
The IRED driver 71 is controlled to measure the distance to each part in the screen.

The distance measuring light projected in this manner is reflected on a subject (not shown), and the two light receiving lenses 57, 5
An image is formed on the PSDs 54 and 55 via the image pickup device 8. From the distance measuring lights incident on the PSDs 54 and 55, two current signals of outputs corresponding to the incident positions of the lights are output by the function of the PSD. These current signals are the preamplifier 8
The compression diodes 84, 85, 86, 8 are absorbed by 0, 81, 82, 83 with a low input impedance and are amplified.
Input to 7.

The compression voltages generated in the compression diodes 84, 85, 86, 87 are supplied to the buffer circuits 88, 89, 90,
At 91, the reference voltage _{Vref is} applied to the bases of the NPN transistors 92, 93, 94 and 95, respectively. NPN
The transistors 92 and 93, and 94 and 95 respectively form a differential circuit in which their emitters are commonly connected.
The emitters of these NPN transistors have I
Current sources 96 and 97 capable of supplying or stopping a predetermined current value in synchronization with the light emission of the RED 53 are connected. The collectors of the NPN transistors 93 and 94 are connected to Vcc, and the NPN transistors 92 and 9 are connected.
The collector of 5 is connected to Vcc via an integrating capacitor 98. The output voltage of the integrating capacitor 98 is controlled by the CPU 62, and the switch 9
Initialization is possible with 9.

In this way, the two output currents of the PSDs 54 and 55 are compressed and input to the differential circuit, so the collector currents of the NPN transistors 92 and 95 are
The output is proportional to the signal light incident position of each PSD. Let these collector currents be I ₉₂ and I ₉₅ .

Here, using the symbols shown in FIG. 18A, I ₉₂ = A ₉₂ · (a + y ₅₄ ) I ₉₅ = A ₉₅ · (a + y ₅₅ ) ... (17) where A ₉₂ , A ₉₅ : Since it is a proportionality constant, if A ₉₂ = A ₉₅ , the integration capacitor 98 is generated when the switch 99 is turned off and the IRED 53 is caused to emit light.
The voltage V ₉₈ generated at V ₉₈ = A ₉₂ (2a + y ₅₄ + y ₅₅ ) · B ₉₈ (18) where B _{98 is a} proportional constant. That is, since the relationship is expressed by the equation (19), when the CPU 62 inputs this V ₉₈ by the built-in A / D converter, y ₅₄ + y ₅₅ is obtained from V ₉₈ .

[0082]

[Equation 2] Therefore, the subject distance L can be calculated as L = S · f _J / (y ₅₄ + y ₅₅ ) ... (20).

When distance measurement is performed on a landscape or the like, the reflected signal light from the subject may not enter the PSD. In this case, if the signal light is low, the output voltage of the compression diode will be low,
Distance measurement calculation is performed due to noise. Since this calculation result is of course irrelevant to the correct subject distance, the compression diodes 85 and 87 are compared by the comparison circuits 100 and 101.
Output voltage is determined. When the output voltage is lower than the predetermined level, the comparison circuit outputs a determination signal to the CPU 62. Therefore, when the CPU 62 detects this signal, it ignores the output voltage of the integrating capacitor 98 and determines that the subject distance is infinity, for example.

Reference numeral 102 denotes 55 in FIG. 18 (b).
It is the inclination adjusting circuit described as a and 55b. Figure 2
Reference numeral 1 is for explaining the adjusting circuit 102. For example, as shown in FIG.
In some cases, the positional relationship between the light receiving lenses 57 and 58 and the PSDs 54 and 55 does not match correctly. That is, f _J54 to f
_The perfect match with _J55 is also due to PSD assembly.
It is also difficult to perfectly match the inclinations θ ₅₄ and θ ₅₅ .

Such an assembling error is shown in FIG.
8 (b) leads to a tilt error of the AF result, but in order to perform the tilt adjustment by mechanically adjusting this,
Since it is necessary to prepare a dedicated adjusting mechanism, it tends to be expensive and the adjusting time tends to be long. Therefore,
In order to adjust this electrically, the adjusting circuits 102 and E
EPROM 65 is used.

More specifically, the adjusting circuit 102 is configured as shown in FIG.
1 (a), the current value of the current source 96 is switched. Current source 9
When the current value of 6 changes, the collector current I ₉₂ of the NPN transistor ₉₂ and the proportional constant A ₉₂ of the light position y ₅₄ incident on the PSD ₅₄ can be changed. Therefore, even if the proportional constant A ₉₂ does not match the proportional constant A ₉₅ of the other light receiving system due to the assembly of PSD,
This can be adjusted electrically to enable correct distance measurement.

The current source 96 is composed of an NPN transistor as shown in the figure, and forms a current mirror circuit together with the NPN transistor 103. In the NPN transistor 103, the collector and the base are short-circuited, and the five constant current sources 104 and 1 are connected to the collector.
05, 106, 107 and 108 are connected. 10
The four current sources 105 to 108 out of 4 to 108 are
ON / OFF is controlled by a counter circuit including flip-flops 109, 110, 111, and 112.

The CPU 62 causes the counter circuit to CK
By input-controlling the (clock) signal and the Reset (reset) signal, each current source can be turned on / off. When a predetermined clock is input to the CK terminal of this counter circuit in the state of the reset signal L (low level), as shown in FIG.
The current value I _INT flowing through the collectors of 3 and 96 changes.

Therefore, at the time of assembling the apparatus, the difference between A ₉₂ and A ₉₅ based on the PSD assembling error or the like is detected, and the value of I _INT enough to cancel the difference is calculated, and this value is equivalent to this clock number. Value that can be written electrically to ROM (EEP
It may be stored in the ROM) 65.

Note that the transistor 113 shown in FIG.
Is a switch for turning on / off the current source 96 in synchronization with the light emission of the IRED. In addition, FIG.
When there is a slope as shown in θ ₅₄ and θ ₅₅ in (c),
When IRED is scanned in the x direction, the AF result changes even if the subject distances are the same. Therefore, FIG.
It becomes impossible to obtain a graph that does not change with respect to x as shown in (c).

Therefore, the EEPROM 65 has an IRED.
A correction coefficient for canceling this error is input in advance for the scan position of. The CPU 62 can detect the scan position x from the rotation speeds of the initial position switch 79 and the motor 73 (see FIG. 20). This EEPR is the distance measurement result obtained when the distance x is measured.
It is entered in the OM. If correction is made with a correction value corresponding to x, and then a correct distance measurement result is determined, the PSD assembly process can be simplified and the cost can be reduced.

Next, referring to FIG. 22, two PSDs 5
A method for measuring a distance in a portion other than the range E in which 4 and 55 cannot simultaneously detect will be described. When the IRED 53 projects light from a position shifted by y _LED from the optical axis of the light projecting lens 56, the distance measurement at the object distance L 59 is
The method described above is not sufficient. This is because the reflected signal light from the portion 59 is P even if it is incident on the PSD 54.
This is because y ₅₅ cannot be detected because it does not enter the SD ₅₅ .

However, y of the other PSD 54
_Since the reflected light is incident on ₅₄ , the distance can be measured according to this information. That is, if the distance between the principal points of the light _emitting / receiving lenses 56 and 57 is S ₁ and the focal length of the light receiving lens 57 is f _J , then L = S ₁ · f _J / (y _LED + y ₅₄ ) ... (21)

FIG. 23 is a flow chart for explaining the operation of this distance measuring device which enables distance measurement even in such a case. The operation will be described below according to this flowchart. First, in step S41, the position y of the IRED 53 is set.
_The CPU 62 switches the _LED to the initial position switch 79 and the motor 7.
It detects from the number of rotations of 3. Next, in steps S42 and S43, the value of y _LED is determined. Here, only when y _LED satisfies the condition of −y _g ≦ y _LED ≦ y _g , the process proceeds to the distance measuring process using PSDs 54 and 55 after step S44. Note that the above-y _g and y _g represent the limit of the position of the y _LED for allowing the distance measuring light 59 to enter the shaded area E in FIG.

In step S44, the light emission of the IRED 53 is started, and subsequently, in steps S45 and S46, the signal light incident positions y are respectively set by the two PSDs 54 and 55.
_The current sources 96 and 97 are turned on so that the integration operation for detecting ₅₄ and y ₅₅ is performed. Then, the signal is integrated into the integrating capacitor 98, and it is determined in step S47 that the integration for a predetermined time is completed. If it is determined in step S47 that the integration has ended, then in step S48 the IRED53
Flashing ends. Then, in step S49,
The subject distance L is calculated from the charging voltage of the integrating capacitor 98 in accordance with the distance S between both light receiving lenses and y ₅₄ , y ₅₅ .

On the other hand, in step S42, y
_When it is considered that the _LED becomes large and no signal is input to the PSD ₅₄ , the process branches to step S50. Then, after the IRED 53 emits light in step S50, the current source 97 is turned on for the integration operation for detecting the signal light incident position y ₅₅ on the PSD ₅₅ in step S51. Next, in step S52, when the completion of integration after a predetermined time is detected, in step S53 the IRED53 is detected.
The emission end of is controlled. Then, in step S54, y ₅₅ is detected from the integration result, and y _LED and the projection lens 56
The subject distance L is calculated from the distance between the light receiving lens 58 and the light receiving lens 58.

In step S43, y
_{If the LED} is determined to exceed -y _g , then exactly Figure 2
The situation is shown in 2. Therefore, after the IRED 53 emits light in step S55, the current source 97 is turned on in step S56. Next, when the integration end detection after a predetermined time is detected in step S57, the emission end of the IRED 53 is controlled in step S58.
Then, in the same way as step S54, step S
At 59, the subject distance L is calculated from y ₅₄ , y _LED and S ₁ (see FIG. 22).

Thus, the scan position y of the IRED
It is possible to provide a device capable of measuring a wider angle of view by using the _LED and the distance measurement calculation in consideration of the distance between light _emitting and receiving.

[0099]

As described above, according to the present invention, it is possible to provide a distance measuring device capable of accurately measuring a plurality of points on a screen at high speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a concept of a distance measuring device in a first embodiment of the present invention.

FIG. 2 is a diagram showing a distance measuring principle of the distance measuring device of the present invention.

FIG. 3 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.

4A is an external view showing an arrangement in which the distance measuring device shown in FIG. 3 is incorporated in a camera, and FIG. 4B is an example of a distance measuring point that changes two-dimensionally on a photographic screen (finder). It is the figure which showed.

5 is a circuit configuration diagram showing details of the optical position detection circuit of FIG.

6A is a diagram illustrating a method for obtaining a subject distance L from a signal light position on a PSD and the light position detection circuit of FIG. 3;
(B) is a diagram showing an arrangement in the direction (x) connecting the principal points of the light receiving lens and the direction (y) perpendicular thereto on the PSD of FIG.

FIG. 7 is a flowchart illustrating a scan AF operation of the distance measuring device.

FIG. 8 is a subroutine for explaining the distance measuring operation in step S6 of FIG.

FIG. 9 is a diagram showing an example of scanning distance measuring points.

FIG. 10 is a diagram showing an example of a scene in which no subject is present at a point in the center of the screen.

FIG. 11 is a diagram showing an example of a scene in which a main subject is present in the center of the screen including a miscellaneous subject.

FIG. 12 (a) is a third embodiment of the present invention and is a front view showing an arrangement in which a distance measuring device is incorporated in a camera, and FIG. 12 (b) is a conceptual view of the camera of FIG. , (C) are conceptual diagrams showing only the y coordinate of the camera of FIG.

FIG. 13 is a third diagram that emphasizes the distance measurement result L _MNO at the center of the screen.
3 is a flowchart illustrating the operation of the embodiment of FIG.

FIG. 14 is a diagram showing a positional relationship between a viewfinder lens and a light projecting means of a general camera.

FIG. 15 is a diagram showing another configuration example of the optical scanning for distance measurement.

FIG. 16 is a block diagram showing the concept of a distance measuring device in a further embodiment of the present invention.

17 is an external view of a camera equipped with the distance measuring device having the configuration of FIG.

FIG. 18 shows two PSs in a distance measuring device according to a further embodiment.
It is a figure explaining operation | movement of D.

FIG. 19 is a diagram showing a relationship between IRED and distance measuring light in a distance measuring device according to a further embodiment.

FIG. 20 is a block diagram showing a configuration for explaining a further embodiment in more detail.

21A and 21B are diagrams for explaining the details of the adjustment circuit 102 in FIG. 20, where FIG. 21A is a circuit configuration diagram, and FIG. 21B shows the CK number of the counter circuit and the current value I _INT flowing through the collectors of the transistors 103 and 96. FIG. 3C is a diagram showing the relationship, and FIG. 3C is a diagram showing the positional relationship between the light receiving lenses 57 and 58 and the PSDs 54 and 55.

FIG. 22 is a diagram illustrating a method for measuring a distance in a portion other than a range E where two PSDs 54 and 55 cannot simultaneously detect.

23 is a flowchart illustrating an operation of the distance measuring device in FIG. 20.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... CPU, 2 ... Light projecting part, 3 ... Scanning part, 4, 6 ... Light receiving lens, 5, 7 ... Optical position detection element (PSD), 8, 8a,
8b, 9, 9a, 9b ... Optical position detection circuit, 10 ... Distance measuring light spot, 11 ... IRED, 12 ... IRED driver, 13 ... Projection lens, 14 ... IRED holding unit, 15,
19 ... Motor (M) driver, 16, 20 ... Motor, 1
7, 21 ... Feed screw, 18, 23 ... Guide rail, 22
… Supports, 24… Switches.

[Procedure amendment]

[Submission date] January 19, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0090

[Correction method] Change

[Correction content]

Note that the transistor 113 shown in FIG.
Is a switch for turning on / off the current source 96 in synchronization with the light emission of the IRED. In addition, FIG.
When there is a slope as shown in θ ₅₄ and θ ₅₅ in (c),
When the IRED scanned in the x direction, it intends want AF results equal the subject distance is changed. Therefore, FIG.
It becomes impossible to obtain a graph that does not change with respect to x as shown in (c).

Claims (3)

[Claims] 1. A light projecting means for projecting a light beam toward an object, a scanning means for scanning the light projecting means, and a first signal for outputting a first signal according to an incident position of reflected light from the object. Light receiving means, a second light receiving means for outputting a second signal according to an incident position of reflected light from the subject, and the first signal and the second signal for each position during scanning by the scanning means. A multi-point distance calculating means for calculating a subject distance using the distance measuring apparatus. 2. A light projecting means for projecting a light beam toward an object, and a pair of light projection means arranged at a position separated from the light projecting means by a first predetermined base line length, in accordance with an incident position of reflected light from the object. A first light receiving element that outputs a first signal, and a pair of second signals that are arranged at a position separated from the light projecting unit by a second predetermined base line length and that corresponds to the incident position of the reflected light from the subject. A second light receiving element; a first calculation means for calculating a ratio of the pair of first signals; a second calculation means for calculating a ratio of the pair of second signals; A distance measuring device, comprising: an integrating circuit that adds and integrates the ratio calculations output from the second calculating means. 3. A correction means for electrically correcting variation in at least one of the output characteristics of the first calculation means or the second calculation means for performing the ratio calculation is further provided. The distance measuring device according to claim 2.